The present invention relates to a method for fabricating a low resistive electrode for an extendable high-κ metal gate (HKMG) stack, and more specifically, to fabricating a metal gate electrode using cobalt.
The metal oxide semiconductor field effect transistor (MOSFET) is a transistor used for amplifying or switching electronic signals. The MOSFET has a source, a drain, and a gate electrode of metal or metal oxide. The metal gate is electrically insulated from the main semiconductor n-channel or p-channel by a thin layer of insulating material, for example, silicon dioxide, glass, or high κ material such as titanium nitride, which makes the input resistance of the MOSFET relatively high. The metal gate stack includes the metal gate, the insulating layer, and possibly other layers. The gate voltage controls whether the path from drain to source is an open circuit (“off”) or a resistive path (“on”). When the gate electrode is made smaller to allow smaller devices, the smaller critical dimension (CD) of the gate results in increased resistivity of the metal gate stack.
N-type field effect transistors (nFET) and p-type field effect transistors (pFET) are two types of complementary MOSFETs. The nFET uses electrons as the current carriers and with n-doped source and drain junctions. The pFET uses holes as the current carriers and with p-doped source and drain junctions.
Some devices, such as complementary metal oxide semiconductors (CMOS) have both nFET and pFET transistors, usually mounted on the same substrate.